Solid-state ignition systems are known in the art. U.S. Pat. No. 5,065,073 (hereinafter "the '073 patent"), which is hereby incorporated by reference, teaches that improved control over the performance of an ignition system can be achieved by incorporating a solid-state switch into an ignition output circuit. As taught by the '073 patent, the ability of a solid-state switch to be triggered at a precise time allows an ignition system incorporating such a switch to achieve controlled spark rates. As explained in the '073 patent, the control of the spark rate may be accomplished by inserting a time delay into the sequence of events generating successive sparks. The sequence is: charge an energy storage device which is most generally a capacitor, rapidly discharge that energy through a switch to a sparking device, wait for a predetermined period of time before again charging the energy storage device for the next spark. These three events have relatively different times associated with them. Generally, the charge cycle is accomplished in a few tens of milliseconds, whereas the discharge event is instantaneous in comparison, lasting only a few hundred microseconds, and the waiting time is several times longer than the charge time. This sequence is characterized by a large ratio of peak power versus average power demanded from the input. The power demand, and consequently the input current, is relatively higher during the charge cycle and lower, nearly none, during the waiting time between charge cycles.
It is common in the art of ignition systems to design an apparatus with multiple redundant channels to increase the reliability of ignition. When such multi-channel apparatus is designed according to the teachings of the above referenced patent, the power demand ratio is further accentuated. For example, in a dual channel system, immediately following application of input power both channels demand current for their charge cycles at the same time. Aside from minor imbalances in the channels, the charge cycles are of similar duration, the channels discharge at approximately the same time, and they both wait during the same period of time before resuming their respective charge cycles. These overlapping charge cycles effectively double both the magnitude of the total peak demand and the peak-to-average power demand ratio.
The '073 patent also teaches that increasing the repetition rate for a period of time following application of input power provides a burst of sparks synchronized with engine start-up. The power demanded during the burst period is several times higher than that required after the burst period terminates. In an ignition system with multiple channels, especially if it includes a burst-of-sparks feature, there is a further increased demand on the power source for the ignition apparatus. The surge of power and current immediately following application of power may be in excess of practical limitations imposed by the wiring, overcurrent protection devices, and the capacity of the power source.